mouse-models-of-helicobacter-infection-and-gastric-pathologies

Mouse Models Of <em>Helicobacter</em> Infection And Gastric Pathologies

Helicobacter pylori is a gastric pathogen that is present in half of the global population and is a significant cause of morbidity and mortality in ...

Hudson institute of Medical Research

Persistent stomach infection with Helicobacter pylori causes chronic mucosal inflammation (gastritis), which is widely recognized as an essential precursor to gastric cancer. The IL-1 interleukin family cytokines IL-1β and IL-18 have emerged as central mediators of mucosal inflammation. Here, we review the regulation and functions of these cytokines in H. pylori-induced inflammation and carcinogenesis.

Regulation and functions of inflammasome-mediated cytokines in Helicobacter pylori infection.

The gastrointestinal epithelium provides the first line of defense against invading pathogens, among which Helicobacter pylori is linked to numerous gastric pathologies, including chronic gastritis and cancer. Primary gastric epithelial cells represent a useful model for the investigation of the underlying molecular and cellular mechanisms involved in these H. pylori associated diseases. In this chapter, we describe a method for the isolation of primary gastric epithelial cells from mice and detection of epithelial cell adhesion molecule (EpCAM) expression in the isolated cells.

Isolation of Mouse Primary Gastric Epithelial Cells to Investigate the Mechanisms of Helicobacter pylori Associated Disease.

Helicobacter pylori (H. pylori) causes chronic inflammation which is a key precursor to gastric carcinogenesis. It has been suggested that H. pylori may limit this immunopathology by inducing the production of interleukin 33 (IL-33) in gastric epithelial cells, thus promoting T helper 2 immune responses. The molecular mechanism underlying IL-33 production in response to H. pylori infection, however, remains unknown. In this study, we demonstrate that H. pylori activates signalling via the pathogen recognition molecule Nucleotide-Binding Oligomerisation Domain-Containing Protein 1 (NOD1) and its adaptor protein receptor-interacting serine-threonine Kinase 2, to promote production of both full-length and processed IL-33 in gastric epithelial cells. Furthermore, IL-33 responses were dependent on the actions of the H. pylori Type IV secretion system, required for activation of the NOD1 pathway, as well as on the Type IV secretion system effector protein, CagA. Importantly, Nod1 mice with chronic H. pylori infection exhibited significantly increased gastric IL-33 and splenic IL-13 responses, but decreased IFN-γ responses, when compared with Nod1 animals. Collectively, our data identify NOD1 as an important regulator of mucosal IL-33 responses in H. pylori infection. We suggest that NOD1 may play a role in protection against excessive inflammation.

NOD1 is required for Helicobacter pylori induction of IL-33 responses in gastric epithelial cells.

Outer membrane vesicles (OMVs) are constitutively produced by Gram-negative bacteria both in vivo and in vitro. These lipid-bound structures carry a range of immunogenic components derived from the parent cell, which are transported into host target cells and activate the innate immune system. Recent advances in the field have shed light on some of the multifaceted roles of OMVs in host-pathogen interactions. In this study, we investigated the ability of OMVs from two clinically important pathogens, Pseudomonas aeruginosa and Helicobacter pylori, to activate canonical and noncanonical inflammasomes. P. aeruginosa OMVs induced inflammasome activation in mouse macrophages, as evidenced by "speck" formation, as well as the cleavage and secretion of interleukin-1β and caspase-1. These responses were independent of AIM2 and NLRC4 canonical inflammasomes, but dependent on the noncanonical caspase-11 pathway. Moreover, P. aeruginosa OMVs alone were able to activate the inflammasome in a TLR-dependent manner, without requiring an exogenous priming signal. In contrast, H. pylori OMVs were not able to induce inflammasome activation in macrophages. Using CRISPR/Cas9 knockout THP-1 cells lacking the human caspase-11 homologs, caspase-4 and -5,we demonstrated that caspase-5 but not caspase-4 is required for inflammasome activation by P. aeruginosa OMVs in human monocytes. In contrast, free P. aeruginosa lipopolysaccharide (LPS) transfected into cells induced inflammasome responses via caspase-4. This suggests that caspase-4 and caspase-5 differentially recognize LPS depending on its physical form or route of delivery into the cell. These findings have relevance to Gram-negative infections in humans and the use of OMVs as novel vaccines.

Le Son Tran

Centre for Innate Immunity and Infectious Diseases

Hudson institute of Medical Research

Mouse Models Of Helicobacter Infection And Gastric Pathologies

Le Son Tran

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Hudson institute of Medical Research

Mouse Models Of Helicobacter Infection And Gastric Pathologies

Centre for Innate Immunity and Infectious Diseases